Update to CentOS 6.5
Remove commented line.
Don't disable postfix

Who did that? :$
Misusing the -i option. Split up the params
Be more specific with keeping en_US locales
Lines >80 are generally harder to follow...
Importing key before yum runs stops a warning
Be less opinionated over what to install
Remove software required by GA after it's installed

It's unlikely most of us will be installing kernel drivers so
those that need it can reinstall it.
A few cleanups for the README